Dual biological activity of apurinic acid on human lymphocytes: induction of interferon-gamma and protection from human immunodeficiency virus infection in vitro

Current Findings Regarding Natural Components With Potential Anti-2019-nCoV Activity

COVID-19, a novel coronavirus pneumonia (named by the World Health Organization, WHO), has spread widely since the end of 2019. Research on synthetic drugs and vaccines has become a focus of attention in China and other countries, as such approaches are regarded as key tools for disease prevention and control; however, the development of these therapeutics will take months, or even years. Under such circumstances, development of coronavirus specific therapeutics is urgent. For this specific indication, the rapid performance of natural products, such as plant compounds, herbal extracts, and traditional Chinese medicine, could contribute as alternative measures. Recent investigations have provided evidence that these natural products are potential candidates for development as therapeutic agents against the virus that causes COVID-19, 2019-nCoV. Targeting the structural proteins or cellular receptors of 2019-nCoV, including coronavirus chymotrypsin-like (3CLpro or Mpro), helicase (nsP13), S protein, and human angiotensin converting enzyme 2 (ACE2), holds promise for preventing infection. In this review, we summarize some representative natural products and their active components that have potential anti-2019-nCoV effects. We focus on the basic structural elements of 2019-nCoV, its main mechanisms of action, and the feasibility and potential of products to inhibit the novel coronavirus. In addition, the relative advantages, additional functions, and precautions that should be used with typical natural products are also discussed. The aim is to make the case that natural products could be a valuable pool for the development of active compounds for treating 2019-nCoV infection, which may contribute to mitigation of the spread of the pandemic.

Synergistic Anti-Human Immunodeficiency Viral (HIV-1) Effect of the Immunomodulator Ampligen (Mismatched Double-Stranded RNA) with Inhibitors of Reverse Transcriptase and HIV-1 Regulatory Proteins

The potent antiviral effect of double stranded RNA, such as the mismatched poly(l)·poly(C12U) [Ampligen], 2′,3′-dideoxy-3′-fluorothymidine (FddThd) and antisense oligodeoxynucleotides (ODN) has been established in in vitro systems using cells infected with the human immunodeficiency virus type 1 (HIV-1). We report here that the immunomodulator poly(l)·poly(C12U) interacts synergistically with (1) the reverse transcriptase inhibitor FddThd (FIC value: 0.43), (2) the modified (5′- and 3′-end capped thioates) antisense ODN-4 directed against the splice acceptor site of the HIV-1/ tat gene (FIC value: 0.66) and (3) also with pyronin Y, a compound which prevents binding of HIV-1 Rev protein to the HIV-1 RRE element. These data suggest that combinations of poly(l)·poly(C12U), a stimulator of the natural antiviral protection system of the cells, with compounds targeting HIV1-specific processes should be considered as candidate treatments of AIDS patients.

Abnormalities in serum concentrations of interleukin-2, interferon-alpha and interferon-gamma in schizophrenia not detected

The hypothesis of an immunological defect in schizophrenia has been supported by reports on abnormal production of interleukin-2 (IL-2) and interferons (IFNs) in schizophrenic patients. In the present study we determined the serum concentrations of IL-2, IFN-alpha and IFN-gamma in 10 first onset, neuroleptic-naive schizophrenics, in 6 pretreated patients who were drug free (1 week to 2 years) at the time of the investigation and in 15 matched healthy controls. No IFN-alpha was detected in schizophrenics' and in control sera. No differences were found in IL-2 and IFN-gamma levels between schizophrenics and controls. Thus the present study failed to support the hypothesis of an immunological abnormality in schizophrenia on the basis of the determination of IL-2 and IFNs serum levels.

(2'-5')Oligoadenylate and intracellular immunity against retrovirus infection

1. The double-stranded RNA-dependent 2',5'-oligoadenylate (2-5A) synthetase/ribonuclease L (RNase L) system plays an essential role in the establishment of the antiviral state of a cell exposed to virus infection. 2. Until recently, the application of 2-5A derivatives to reinforce this system seemed to be limited mainly due to the low specificity of RNase L for viral RNA. 3. Two new strategies have been developed which yield a selective antiviral effect of 2-5As at least against human immunodeficiency virus-1 (HIV-1) infection: (i) an "intracellular immunization" approach using 2-5A synthetase cDNA linked to HIV trans-acting response element (TAR) and (ii) inhibition of retroviral reverse transcriptase activity by 2-5A analogues.

Human immunodeficiency virus: novel enzyme-linked immunoassays for quantitation of envelope glycoprotein 120

Two novel enzyme-linked immunoassays (ELISA) for the quantitation of human immunodeficiency virus type 1 (HIV-1) coded glycoprotein with an Mr 120 (gp120) are described. These are based on the highly specific interaction between gp120 and the mannose-specific lectins from Narcissus pseudonarcissus (NPL) and Galanthus nivalis (GNL). Two systems were developed: (1) an HIV-protein ELISA using HIV-protein (also containing HIV-gp120) for the solid phase and NPL as a detector and (2) a lectin-ELISA using the NPL bound to the solid phase and GNL as detector. The HIV-protein ELISA was validated for quantitation of gp120 within the range 3 to 600 ng/ml; the lectin-ELISA for concentrations between 0.6 and 20000 ng gp120/ml. Serum components did not interfere with the binding of gp120 to the lectins. The ELISAs were used for the quantitation of gp120 in HIV-infected CEM cells in vitro. It was found that gp120 appeared in the medium earlier after infection than HIV-p24 and reverse transcriptase, suggesting that gp120 is released as free glycoprotein. Moreover, the ELISAs were also applied successfully for the detection of compounds that bind to gp120 and for the identification of antibodies directed against the highly pathogenic mannan portion of gp120. These ELISAs are considered to be suitable also for the detection of gp120 in the serum of HIV-infected individuals.

Cordycepin analogues of 2',5'-oligoadenylate inhibit human immunodeficiency virus infection via inhibition of reverse transcriptase

Analogues of 2',5'-oligoadenylates (2-5A), the cordycepin (3'-deoxyadenosine) core trimer (Co3) and its 5'-monophosphate derivative (pCo3), were shown to display pronounced anti-human immunodeficiency virus type 1 (HIV-1) activity in vitro. Treatment of HIV-1 infected H9 cells with 1 microM Co3 or pCo3 resulted in an almost 100% inhibition of virus production. The compounds were encapsulated in liposomes targeted by antibodies specific for the T-cell receptor molecule CD3. Substitution of one or two cordycepin units in Co3 or pCo3 decreased the antiviral activity of the compounds. pCo3 did not stimulate 2-5A-dependent ribonuclease L activity and displayed no effect on the amount of cellular RNA and protein. At a concentration of 10 microM the cellular DNA polymerases alpha, beta, and gamma were almost insensitive toward Co3 or pCo3. In contrast, these compounds reduced the activity of HIV-1 reverse transcriptase (RT) by 90% at a concentration of 10 microM if the viral RNA genome and the cellular tRNALys.3 was used as template/primer system; if the synthetic poly(A).(dT)10 was used as template/primer, no marked inhibition was observed. Dot-blot, gel-retardation, and cross-linking assays showed that Co3 or pCo3 interfere with the binding site of tRNALys.3 to RT. These results indicate that inhibition of RT at the level of initiation of the enzymic reaction is a novel approach to inhibit HIV-1 replication.

Inhibitory effect of nonviable preparations from human immunodeficiency virus 1 on inositol phospholipid metabolism

Previously it was established [Pahwa, S., Pahwa, R., Saxinger, C., Gallo, R. C. & Good, R. A. (1985) Proc. Natl. Acad. Sci. USA 82, 8198] that nonviable preparations of human immunodeficiency virus 1 (HIV-1) abolish the proliferative response of human lymphocytes to phytohemagglutinin A. Now we describe that this effect might be, at least partially, due to an impairment of the function of phospholipase C. It was found that addition of HIV-1 preparation to lymphocytes diminished the stimulation of phosphatidylinositol phosphorylation caused by phytohemagglutinin A. Moreover, this preparation completely abolished the phytohemagglutinin-A-stimulated release of inositol trisphosphate and prevented a translocation of protein kinase C from cytosol to membranes. From this data we conclude that nonviable HIV-1 preparations inhibit the intracellular signalling pathway, leading to a reduced mitogenic response to phytohemagglutinin A, at the level of protein kinase C.

Association of Tat protein and viral mRNA with nuclear matrix from HIV-1-infected H9 cells

The transactivating protein from human immunodeficiency virus type 1 (HIV-1), Tat, was found to bind to the nuclear matrix from uninfected and HIV-1-infected H9 cells. Addition of the Zn2+, Cd2+ and Cu2+ chelator o-phenanthroline destroyed the matrix fibrils and the binding affinity of Tat to the matrix. A sequential treatment of the matrix, first with o-phenanthroline and then with ZnCl2, partially restored the fibrillar-like matrix structure. Infection of H9 cells with HIV-1 resulted in a displacement of cellular mRNA by viral mRNA from the nuclear matrix. Both the matrix-bound host cell and HIV-1 mRNA were found to dissociate from the matrix in the presence of o-phenanthroline. This could be prevented by coincubation with Zn2+ or Cu2+ (but not Mg2+), which stabilize the mRNA containing nuclear matrix structure.